1. Field of Invention
The present invention discloses a preparation method of nano-gold-silver cerium dioxide-supported catalysts and a process of oxidation of carbon monoxide (CO) in air to remove CO using the nano-gold-silver cerium dioxide-supported catalysts. The gold loading is between 0.5 and 5 wt. %. Gold and silver particle sizes are between 1 and 3 nm, and Au/Ag weight ratio is between 1 and 10. Oxidation of CO in air over these catalysts is carried out in a fixed bed reactor to remove CO.
2. Related Art
Some disclosures related to gold catalyst is applied to oxidation of CO and never taught to use bimetallic gold-silver cerium dioxide-supported catalysts and to induce the reaction under 100° C. or less. The precious metal catalysts, such as Pt or Au, is used in the oxidation of CO (J. Power Sources Vol. 135 (2004), pages 177-183; Journal of Power Sources, Vol. 165 (2007), pages 353-358; Catalysis Letter, Vol. 127 (2009), pages 339-347). However, the extremely high prices limit the application of the precious metal catalysts. In general, the gold catalysts must carry 3 wt. % gold or more to achieve the desired activity. Thus, it is desired to add some cheaper metals to increase the activity. For example, the activity of gold-CeO2 catalysts can be improved by adding silver, which is cheaper than gold. The precious metal catalysts were improved by the following method (Journal of Catalysis, Vol. 281 (2011), pages 40-49). The bimetallic Ag—Co catalysts are prepared by coprecipitation method. After the calcining process at different temperatures, the bimetallic Ag—Co catalysts may have different CO oxidation activities, selectivities, and XRD results. Based on the XRD results, the calcining process at 200° C. can combine Ag and Co to form a compound AgCoO2, and the catalysts have the largest surface area. Besides, since Ag and Co are combined to form a compound AgCoO2, the CO oxidation activity of the calcined bimetallic Ag—Co catalysts is increased.
Some other disclosures regarding to the gold catalyst application will be described hereinafter. Taiwan Patent Publication No. 200613048 discloses a preparation of nano-gold ceria-supported catalysts and its application in CO removal in gas. U.S. Pat. No. 5,258,340 discloses a mixed transition metal oxide catalysts for conversion of carbon monoxide and method for producing the catalysts. The published references never disclose the feature of the present invention that uses nano-gold-silver catalysts supported on CeO2 to preferential oxidize CO.